Protective and decorative nickel coatings



at iph United States Patent 3,009,238 PROTECTIVE AND DECORATIVE NICKELCOATINGS Waclaw A. Wesley, Plain'field, and Burton B. Knapp, Westfield,N.J., and Robert J. McKay, Onancock, Va., assignors to The InternationalNickel Company, Inc., New York, N.Y., a corporation of Delaware NoDrawing. Filed Dec. 3, 1957, Ser. No. 700,263 Claims. (Cl. 29-1966) Thepresent invention relates to the provision of decorative and protectivemetallic coatings and, more particularly, to the provision on metallicsurfaces of bright composite electrodeposited coatings which havesubstantially improved resistance to the destructive influences ofindustrial and marine atmospheres and which exhibit an attractive anddecorative surface appearance for long periods of time during use.

As is well known to those skilled in the art, many proposals have beenmade in an endeavor to provide metallic coatings capable of providingappreciable resistance to corrosive attack when subjected to variousatmospheres while retaining a pleasing and decorative surfaceappearance. The bright metallic appearance and, particularly, theretention thereof, of parts of many manufactured articles, e.g.,automobiles, household equipment, metal furniture, etc., is often aparamount consideration in their usefulness and pleasure afforded theuser. However, the various metals and metal combinations which have beenproposed in attempts to satisfy commercial needs have provenunsatisfactory in many applications.

Electrodep'osited chromium is pleasing in appearance and offers a degreeof resistance to corrosive atmospheres but fails to provide sufficientprotection for underlying metals, e.g., ferrous metals, chiefly onaccount of the inherent porosity characterizing chromiumelectrodeposits. Electrodeposited nickel may also have a bright andpleasing appearance but nickel deposits on basis metals arecharacterized by fogging in industrial atmospheres and then by pittingat myriads of points on the surface. It has been proposed heretofore toemploy composite electrodeposited metal coatings, such asnickel-chromium and copper-nickel-chrornium coatings wherein thechromium is the outer layer of the composite, on ferrous metals toprovide an improved combination of corrosion resistance and pleasingappearance while using a commercially practicable thickness of coatingin the neigh borho'od of about 1 mil. However, the corrosion resistanceof these prior composite coatings on steel is still unsatisfactory inapplications requiring relatively long exposure to weathering inindustrial atmospheres, marine atmospheres and other corrosive media.For example, in the commercially used conventional nickel-chromiumcomposite, the thickness of which is generally about 1 mil for economicreasons, chromium reduces the fogging tendency of nickel but thechromium layer is thin and not impervious to atmospheric and othercorrosive effects and, as a consequence thereof; exposure to atmospherescontaining detrimental and corrosive substances, e.g., sulfur dioxide,leads to pitting and/or perforation of the composite coating. When thesepits and/ or perforations penetrate through the coating to the basismetal, e.g., steel, the latter corrodes and unsightly corrosive productsexude to the surface to mar its outward appearance. The protective valueof conventional composite nickel-chromium coatings increases withincreasing thickness of the nickel deposit, but commercially this hasnot proved to be a panacea for rust spotting of the plated metal, e.g.,steel, exposed to weather.

It has been proposed to employ other composite electrodeposited coatingssuch as those containing a coppertin alloy or a copper-zinc alloy layeras a substitute for the nickel layer in the usual nickel-chromiumcomposites. When subjected to weathering, these substitute compositeshave been found to lose their decorative appearance more quickly thanthe conventional composites. Electrodeposited composite coatings such asnickel-copper-nickel have been widely suggested for purposes ofprotecting steel from corrosive elfects but it has been found that thistype of coating is adversely affected by atmospheric attack and that thecorrosion products of copper are themselves highly corrosive to thecoating. Coatings which are customarily used without a surface finish ofchromium, such as zinc and cadmium coatings, although bright whenfreshly prepared become dull rapidly through weathering and/ or wear.

Although many attempts were made to overcome the foregoing difiicultiesand other difiiculties, none, as far as we are aware, was entirelysuccessful when carried into practice commercially on an industrialscale.

It has now been discovered that bright, decorative and protectivecomposite electrodeposited coatings which, when compared withconventional coatings of the same magnitude of thickness, manifest amarkedly higher order of resistance to atmospheric attack, betterprotect the ferrous metal base from corrosion and longer retain apleasing surface appearance during use can be obtained when metal of aselected class is interposed between layers of nickel in the fashion ofa sandwich, the outermost nickel layer advantageously being providedwith a layer of chromium.

It is an object of the present invention to provide compositeelectrodeposited coatings which are bright and decorative and exhibit animproved high degree of corrosion resistance when exposed to atmosphericattack.

Another object of the invention is to provide metallic surfacesincluding metals and/or alloys with composite electrodeposited coatingscharacterized by a high degree of resistance to corrosion when subjectedto weathering and which retain a decorative and pleasing surfaceappearance for relatively long periods of time during use.

The invention also contemplates providing bright, decorative andprotective composite electrodeposited coatings on metallic surfacesincluding metals and/0r alloys which, when compared to conventionalcomposite coatings of comparable thickness, manifest an improved orderof resistance to perforation by corrosive atmospheres, better protectionof the metallic surface from corrosion and longer retention of adecorative and pleasing surface appearance during use.

The invention further contemplates providing a process for accomplishingthe foregoing objects.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the composite electrodeposited coatings provided inaccordance with the present invention are comprised of a plurality ofelectrodeposited nickel layers and a layer of electrodepositeddissimilar metal selected from the group consisting of cobalt, alloys ofcobalt with up to 20% tungsten and up to nickel, tin, lead, silver andpalladium interposed between said layers of nickel. Binary alloys ofcobalt with about 10% to 20% tungsten and about 50% to 90% nickel may advantageously be employed in the interposed or intermediate layer. Arelatively thin layer of chromium having a thickness of about 10 to 20micro-inches is advantageously deposited on the outermost layer ofnickel to contribute stain resistance to the composite coating. When thecomposite coatings of the present invention are electrodeposited on ametallic base, including metals and/or alloys, it has been found thatthe coatings are more resistant to atmospheric and other corrosiveeifects and retain a pleasing protective surface appearance longerduring use than do known bright coatings of the same order of thickness,e.g., the conventional nickel-chromium and copper-nickel-chromiumelectrodeposits. It is important within the concepts of the presentinvention in order to insure the attainment of highly satisfactoryresults that the respective thicknesses of each of the electrodepositedmetal layers comprising the composite coating be controlled with thefollowing ranges:

Mils Basis layer of electrodeposited nickel 0.1 to2 Intermediateelectrodeposited layer of dissimilar metal 0.01 to 0.3 Outer layer ofelectrodeposited nickel 0.1 to 2 The composite coating must in all casesbe at least 0.25 mil thick.

In carrying the invention into practice, it is advantageous in order toachieve optimum results to control the thicknesses of the respectiveintermediate layers or deposits over the following ranges: cobalt, about0.01 to about 0.1 mil; cobalt-nickel alloy, about 0.1 to about 0.3 mil;cobalt-tungsten alloy, about 0.05 to about 0.2 mil; tin, about 0.05 or0.1 to about 0.3 mil; lead, about 0.1 to about 0.3 mil; silver, about0.05 to about 0.2 mil; and palladium, about 0.05 to about 0.2 mil. Whenintermediate or interposed layers of the aforementioned kinds andthicknesses are employed, superior results are obtained using a basisnickel layer having a thickness of about 0.1 to 1 mil and an outernickel layer having a thickness of about 0.1 to 2 mils. In general, forbest protective effects, thicker outer nickel layers should be employedwhen the basis nickel layer has a thickness in the lower portion of therange described. For example, when the basis nickel layer is only about0.2 mil or 0.1 mil, or even as thin as about 0.05 mil, the outer nickellayer should be at least about 0.5 mil or, more advantageously, about0.6 or 0.75 or 1 mil thick. The total thickness of nickel in the twolayers should be at least about 0.5 mil but most advantageously is atleast about 1 mil, particularly when the coating is to be subjected tooutdoor exposure. When composite coatings having layer thicknesseswithin the foregoing preferred ranges are employed, we have found thatthe results obtained are not only markedly superior to the resultsobtained utilizing conventional composites having a single layer ofnickel, e.g., nickel-chromium composites, of comparable thickness, e.g.,about 1 mil, but are comparable and often superior to conventionalcomposites, e.g., nickel-chromium, of twice the thickness, e.g., about 2mils. When intermediate, or interposed, layers (sandwiched between thenickel layers) comprised of cobalt, cobalt-nickel alloy orcobalt-tungsten alloy are employed in accordance with the invention, theresulting coatings are superior in corrosion resistance to conventionalnickel-chromium coatings having the same thickness of nickel, and it isthus advantageous to use these metals for the intermediate layer toobtain the most satisfactory results. In many applications, compositecoatings within the invention are superior for decorative and protectivepurposes to conventional nickel-chromium coatings having twice thethickness of nickel. The efiectiveness of composite coatings having aninterposed layer of cobalt or a cobalt-containing alloy increases as thethickness of the intermediate layer is increased up to'.l mil. When thethickness of the interposed cobalt and cobalt-containing alloy layersfalls below the minima set forth herein, the beneficial influence of thecomposite coating is lost and the protective value of the compositecoating drops to that of a single layer of nickel having the samethickness.

The nickel layers contemplated by the invention may be made ofelectrodeposited nickel obtained from plating baths of the conventionalWatts type, or may be made of bright or semi-bright nickel depositedfrom baths containing the usual brighteners and/or levelers forenhancing the smoothness and appearance of the nickel electrodeposit.Nickel plating baths for producing nickel deposits satisfactory for usein the present invention contain up to 400 grams per liter of nickelsulfate (NiSO .7H O), up to 400 grams per liter of nickel chloride (NiCl6H O) and up to 50 grams per liter (preferably 10 to 40 grams per liter)of a buffer such as boric acid. Those skilled in the art know that theessential ingredients of the Wattstype nickel plating bath are nickelsulfate (NiSO -7H O) and nickel chloride (NiCl -6H O) which may bepresent in the bath in amounts of about to about 400 grams per liter andof about 10 to about 60 grams per liter, respectively. The bath isoperated in the pH range of about 1.5 to 6. Usually a buffering agentsuch as boric acid is included in the bath in an amount of up to about50 grams per liter, e.g., about 10 to about 40 grams of boric acid perliter. A small amount (e.g., about 0.2 gram per liter) of a wettingagent such as a sodium lauryl sulfate is usually included in the bath toprevent undesirable pitting. Cathode current densities of about 20 toabout 100 amperes per square foot are usually employed and the operatingrange of bath temperatures is about to about 160 F. Nickel depositedfrom the Watts-type bath generally will require bufiing beforeapplication of the final chromium plate to insure a fully brightappearance. Plating baths for plating bright nickel are of generallysimilar composition to the Watts-type bath and may, for example, containabout 25 to 300 grams per liter of nickel sulfate (NiSO -7H O) and 30 to225 grams per liter of nickel chloride (NiCl -6H O), with up to 50 gramsper liter of boric acid as a buffer. Bright nickel baths includecombinations of addition agents for producing a more lustrous andbrighter deposit than is obtainable with the Watts-type bath. Theseaddition agents generally include a combination of a wetting agent, aleveling and/or smoothing agent, a luster-producing agent and astressreducing agent. Bright nickel plating baths are discussed inModern Electroplating, John Wiley and Sons, Inc., New York, 1953, atpages 311 to 318, and in many US. patents, including, e.g., Patents Nos.2,191,813, 2,389,135, 2,524,619, 2,647,866 and 2,648,628.

Plating baths for producing semi-bright nickel are generally similar incomposition to Watts-type baths and bright nickel baths and contain aleveling agent, such as coumarin and derivatives thereof, whichcontributes a leveling and scratch-covering property to the platewithout introducing a high level of stress therein as may be the casewith bright nickel. Semi-bright nickel plates are not as bright as thebright nickel plates but are more easily buffed than conventionalWatts-type plates and are characterized by a high degree of smoothness.Nickel electrodeposits from the Watts-type bath generally have ahardness of about to Vickers, while bright nickel electrodepositsgenerally have a higher hardness which may be as high as about 500Vickers.

Modern production conditions favor the use of bright or semi-brightnickel deposits since these deposits require no buffing or very littlebutling as compared to the c0nventional gray or Watts-type nickeldeposits. A particular embodiment of the invention wherein asatisfactory composite coating upon an underlying metal, e.g., steel, isprovided without any mechanical polishing operation, e.g., bufling,includes the following steps: (1) prepare the underlying metal forplating, (2) deposit a layer of gray or Watts-type nickel thereon in athickness as hereinbefore described, (3) deposit an intermediate layerof metal of the hereinbefore-described kind and thickness, (4) deposit abright outer nickel layer of the hereinbefore-described thickness and(S) deposit an outer chromium layer over the said bright nickel layer.The aforedcscribed outer nickel layer may advantageously comprise alayer of semi-bright nickel applied over the intermediate layer insufiicient thickness to provide a good leveling action, e.g., about 0.5mil, and a layer thereover of bright nickel to provide a bright finishupon which the final chromium layer may be applied. Alternatively,layers of bright nickel may be employed in accordance with theinvention.

The invention also contemplates multi-layer coatings having a pluralityof electrodeposited intermediate layers of the kind and thicknessdescribed hereinbefore and having a plurality of electrodeposited nickellayers having thicknesses as aforedescribed. As as example, a multilayercomposite on steel comprising a layer on the steel of electrodepositednickel 0.1 mil thick, a layer thereon of electrodeposited cobalt 0.1 milthick, another layer of nickel 0.1 mil thick, a further layer of cobalt0.1 mil thick, and an outer layer of nickel 1 mil thick, with adecorative coating of chromium IO-micro-inches thick is a satisfactorymulti-layer composite in accordance with the invention.

In preparing the composite electrodeposited coatings in accordance withthe invention, it is of the utmost importance that sound adhesion ofeach layer to each other layer be obtained.

In order to demonstrate the improved results achieved in carrying outthe concepts of the present invention, an extensive testing program wasconducted to establish the resistance of composite electrodepositedcoatings within the invention and to compare the resistance toatmosphereic corrosion of these composites with other composites outsidethe scope of the present invention and with control tests ofconventional nickel-chromium electrodeposited coatings. In all cases astain resistant chromium coating about 10 to 20 micro-inches thick wasapplied as the outer layer. Except where otherwise specified, the nickellayers employed were of the conventional Watts type or gray nickel. Dataobtained as a result of this testing program is tabulated hereinafter inTables I to VII. Testing was carried out both in an industrial at.-mosphere at Bayonne, New Jersey, and in a marine atmosphere at KureBeach, North Carolina. The test specimens for the most part wereelectrodeposited upon panels of polished SAE 1010 steel in the form of/s x 4 x 6 plates. One of the sets of test specimens comprised foilswhich were made by electrodepositing coatings to be tested on a highlypolished cobalt-chromium alloy (such as is sold under the trademarkStellite) starting sheet from which electrodeposited foils could easilybe stripped. Conventional cleaning and plating methods well known tothose skilled in the art were employed in the preparation of the testpanels and foils. Thus, the steel panels were prepared for platingaccording to the following procedure.

(1) Polish the panels with grit belts, finishing with a 320-grit belt.

(2) Vapor degrease.

(3) Pumice scrub and hot water rinse.

(4) Cathodically clean in a solution of sodium carbonate containing 60grams per liter Na CO for 25 minutes at 160 F. and 25 amperes per squarefoot.

(5) Anodically clean the panels in the sodium carbonate solution for 5minutes at 20 amperes per square foot.

(6) Dip in a solution containing 50% hydrochloric acid by volume for 30seconds at 105 -115 F.

After exposure of the plated steel panels in the atmospheres and for thetimes indicated in the following tables, the panels were examined tocompare the corrosion resistance of the coatings deposited thereon witheach other and with the nickel-chromium control panels of theconventional type. The examination comprised a visual inspection whereinthe panels were given a merit rating designating the relative order andthe appearance of each panel, with the panel exhibiting the bestappearance being designated by the numeral 1. In addition, the panelswere rated according to the method recommended by the American Societyfor Testing Materials Committee B8, Subcommittee II, described in theProceedings of the A.S.T.M., vol. 49 (1949), at pages 220 et seq. Thismethod involves examination of the test panels to determine thecorrosion-affected area and comparing the panels with standards so thata rating number up to 10 could be assigned thereto.

The following comparison of percentage corrosionafiected area and ratingnumbers was employed in evaluating the panels described in Tables I toVII hereinafter:

Rating number: Corrosion-atfected area, percent The results obtained inthe testing program, as set forth in Tables I to VII, are as follows:

TABLE I Tests of electrodeposits on steel exposed for 18 months in anindustrial atmosphere. This set included composite electrodepositednickel coatings of the sandwich type containing intermediate layers ofcobalt, a cobalt-tungsten alloy containing about 15% tungsten, silver,palladium,

lead, tin, copper, zinc, iron, a nickel-iron alloy containing about 16%iron, and a conventional nickel-chromium composite control panel (panel9). All the coatings were deposited to a thickness of 1 mil to alford acomparison. It was found that, after exposure, the composites containingintermediate layers of cobalt, tin, palladium, cobalt-tungsten alloy andsilver were markedly superior in all respects as compared to theconventional nickelchrornium deposit. On the other hand, the compositescontaining intermediate layers of Zinc, iron-nickel alloy,

copper and iron were inferior to the conventional nickelchrorniumdeposit.

TABLE II Tests on electrodeposited foils exposed for 12 months in anindustrial atmosphere. This set contained composite foils prepared tothe same specifications as the composite coatings set forth in Table I.The foils were prepared upon a polished cobalt-chromium al loy startingsheet which was prepared for plating by vapor degreasing, pumicescrubbing, rinsing, cathodic cleaning at amperes per square foot for 2minutes at 160 F. in a solution containing 60 grams per liter of sodiumcarbonate, and rinsing. After plating, the foils were stripped from thestarting sheet. After exposure, the foils were inspected by placing themagainst a strong light in a darkroom. A No. 2 photoflood bulb was usedin a photographic printing box and the foil was masked to facilitatedetecting and counting of the perforations. Examination of the foilsafter exposure established that the composites containing cobalt,cobalt-tungsten alloy, silver, tin and palladium were substantially moreresistant to perforation as a result of corrosion than was theconventional nickel-chromium foil of the same thickness. It was observedthat the foils containing intermediate layers of zinc, iead, iron-nickelalloy, copper and iron were badly perforated.

TABLE III Steel panels having composite electrodeposited coatingsexposed for 12 months to a marine atmosphere.

This set included 1 mil thick composite electrodeposited coatings of thesandwich type including 0.1 mil thick intermediate layers of acobalt-tungsten alloy containing about 15% tungsten, cobalt, tin, lead,palladium, silver and copper. Panels containing intermediate 0.3 milthick layers of tin (panel 28) and of lead (panel 31) were alsoincluded. A panel having the conventional nickel-chromiumelectrodeposited coating of the same 1 mil thickness was also included(panel 35). Examination of these panels showed that all of the compositecoatings within the invention were superior in corrosion resistance tothe conventional nickel-chromium electrodeposit.

TABLE IV Tests in duplicate of coated steel panels for 12 months in anindustrial atmosphere. This set included sandwichtype compositeelectrodeposited coatings containing intermediate layers of cobalt, tinand silver. All of the layers were deposited to a thickness of 1 mil andthe thickness of the intermediate layer was varied between 0.01 and 0.1mil. Control speciments of conventional nickelchrornium deposits havinga thickness of 1 mil (panel 49) and 2 mils (panel 50) were included. A1.5 mil composite coating containing an intermediate 0.1 mil layer ofcobalt (panel 40) was also included. Inspection of the panels afterexposure demonstrated that the composite coatings containing theintermediate layer of cobalt rated high on the visual inspection but thecomposites containing the thinner cobalt intermediate layers tended tobe low on the A.S.T.M. rating since these composites tended to developblisters. The composites containing the thicker (0.05 and 0.1 mil)cobalt intermediate layers were rated as good as, or better than, theconventional nickelchromium control panels, even those having twice thenickel thickness. It was noted that the composites containing anintermediate layer of tin were prone to develop white stain spots,especially as the thickness of the tin intermediate layer was increased.The composite coatings containing an intermediate layer of sliver 0.05and 0.1 mil thick, respectively, demonstrated an improvement inperformance as compared to the conventional nickelchromium controlpanels having the same thickness.

TABLE V Tests of coated steel panels for 12 months in a marineatmosphere. This set included 1 mil thick sandwich-type compositeelectrodeposited coatings containing intermediate layers of cobalt andtin varying in thickness from 0.01 mil to 0.1 mil. A 1.5 mil compositecoating containing an intermediate layer of cobalt 0.1 mil thick (panel55) was also included. Control steel panels having conventionalnickel-chromium coatings 1 mil (panel 60) and 2 mils (panel 61) thickwere also included. When the panels were examined after exposure it wasfound that all the composite coatings containing cobalt rated well onthe visual examination and demonstrated an improved ability to preventrusting of the underlying steel as compared to the conventionalnickel-chromium control panels. Panel 55, the 1.5 mil thick compositecoating, was rated best on the basis of appearance and protective valueeven as against panel 61, the conventional 2 mil thick coating. Theblistering tendency of the composites containing the cobalt intermediatelayer caused them to be rated low according to the A.S.T.M. system. Thecomposite coatings containing the tin intermediate layers as thin as0.025 mil demonstrated an improved protactive effect as compared to theconventional nickel-chromium control panels.

TABLES VI AND VII Tests in both the industrial (11 months) and themarine months) atmosphere comparing, respectively, the corrosionresistance of sandwich-type composites on steel made, respectively, withbright nickel and with the standard Watts nickel. In the tests describedin Table VI, cobalt in the thickness range from 0.01 mil to 0.1 mil wasused as the intermediate layer in the sandwich-type deposits. In thetests described in Table VII, a cobalt intermediate layer 0.1 mil thickwas included and in the tests described in both Tables VI and VII, acobalt-nickel alloy intermediate layer 0.1 mil thick was included. Thecobait-nickel alloy contained about 50% nickel and in the test describedin Table VI it was deposited in a bright condition while in the testdescribed in Table VII it was deposited in the usual duller graycondition. Control steel panels having a thickness of l, 2 and 3 mils ofbright nickel and of Watts nickel, respectively, and with the usualchromium outer coating, were employed in each series of tests.

The results of the tests indicated that bright nickel is generally asresistant to corrosion as Watts-type nickel. It was again observed thatthe sandwich-type protective and decorative deposits contemplated inaccordance with the present invention, and containing cobalt or acobaltnickel alloy as the intermediate layer, displayed greatly improvedcorrosion resistance, both in the industrial and the marine atmosphere,as compared to a conventional type deposit having the same thickness.

All of the panels were examined in the as-exposed condition since thiscondition represents the appearance of the panels as they would be inuse. Many of the panels were also cleaned and examined again. Cleaningimproved the appearance of the panels but it was noted that, onre-exposure for a relatively short time, the conventionalnickel-chromium control panels exhibited a much greater amount of ruststaining than was the case with the composite coatings containing anintermediate layer embedded in the nickel as contemplated in accordancewith the invention.

Table 1 RESULTS OF EXPOSURE OF COMPOSITE ELECTRO- DEPOSITS ON STEEL TOBAYONNE ATMOSPHERE Set No.1 Po.r1clsNot cleaned Exposure-48 months Finalnickel layer boiled and chromium plated with 15 micro'inchcs oi chromiumOrder of depositing layers Thickness, Visual ASTM mils rating ratingNi-Go-Ni. 4 1-. 5 l 9. 9 N i'Sn-Ni .4.1.5 2 5. 6 NiSn-N i. l. l. 5 3 4.8 Ni-Pd-NL 4. l. 5 4 4. 7 NiCoW-Ni. .4-. l- 5 5 8. 7 Ni-Ag-Ni. .4.1.5 63. 7 .4. l. 5 7 3.5 .4-.1.5 8 2.3 i 9 3. 8 .4.1.5 l0 2. 0 .'i. l. 5 110. 9 .4. l. 5 l2 0 1 Tin layer bufied. 2 Heat treated after plating (2hours at 300 F.).

Table II CORROSION OF COMPOSITE ELECTRODEPOSITED FOILB IN BAYONNEATMOSPHERE Exposure12 months Foil taped on glass plates for exposureFoil size-2" x 4.5

Final nickel layer buffed and chromium plated with 0.000020 inchchromium Pcrforations 3 Panel Order of depositing layers Thickness,

N o. mils 4-. 1- 5 0 0 4. l. 5 2 11 4. l. 5 4 6 4 1. 5 4 1 4'. l. 5 o 04. 1- 5 11 so Ni-Pb-Ni 4. l. 5 630 l, 440 Ni-Zn-Ni .4. l. 5 360 l, Nckel l 3, 330 3, 330 4. 1. 5 13, 500 9, 000 I .4-. 1- 5 1, 740 250Ni-Fc-N 1. 4-. l. 5 540 1,440

1 Tin layer buffed. 2 Heat treated after plating (2 hours at 300 F.). 3Total perforations except where indicated.

9 Table 111 RESULTS OF EXPOSURE OF COMPOSITE ELECTRODE- POSITS ON STEELTO KURE BEACH ATMOSPHERE set Final layer 10 micro-inches of chromiumPanels-Not cleaned 5 Exposure12 months Panel i Hll x Bayonne Kure BeachPane Order of depositing Thickness, (11 months), (10 months), Steel SAE1010 N 0. layers mils ASTM ASTM Final nickel layer bufied and platedwith 20 micro-inches of chromium rating rating Panel Order of depositinglayers Thickness, Visual ASTM Ni-Co-Ni 4 1 5 9 4 No. mils rating ratingNi-Oo-Ni- .45 .05 5 8 4. 5

' N i-Co-Nl. 475-. 025-. 5 9 4. 5

Ni-Co-Ni. .49 01 .5 9 8.5 Ni-CoNi-N 4 1 5 8 4 .4-.1-.5 1 5.1 Nickel 1.05 O .4.1-.5 2 6 -do 2.0 9 7 .4-.1.5 3 8.9 3.0 9 8 2. 3. 4 4-.1-. 5 5 6.8 4-. 1. 5 6 3. 9 2-. 3. 5 7 5.05 ti"? 3 3'1 .4-.1-.5 10 2.1 Table VIICOMPOSITE COATED STEEL PANELS MADE USING WATTS 1 Visual rating in orderoi merit with N o. 1 best.

1 Tin layer bufied.

Table IV POSITS ON STEEL BY BAYONNE ATMOSPHERE Set No.4A and BPanels-Not cleaned Exposure-12 months Final nickel layer buffed andplated with 10-12 micro-inches of chromium Visual ASTM rating ratingPanel Order of depositing Thickness,

No. layers mils Set Set Set Set A B A B 36 Ni-Co-Ni .49 01 .5 11 10 0 01 Visual rating in order of merit, N o. 1 being the best.

Table V RESULTS OF EXPOSURE OF COMPOSITE NICKEL COAT- INGS ON STEEL TOKURE BEACH ATMOSPHERE Set No.6 Panels-Not cleaned Exposure-12 monthsFinal nickel layer bufied and plated with 10-12 micro-inches of chromium1 Visual rating in order of merit, No. 1 being best.

10 Table VI TYPE NICKEL Final nickel layer buffed and plated with 10micro-inches chromium Bayonne Kure Beach Panel Order of depositingThickness, (llmonths), (10 months),

No. layers mils ASTM ASTM rating rating Ni-CoNi-Ni 4-. 1. 5 8 7 Nickel-1.0 1 2 The electroplating baths and conditions of plating employed inproducing the test panels described in Tables I to VII are as follows.

Watts-type nickel bath:

Plating composition- MS-0 .711 0 300 g.p.l. NiCl .6H 0 45 g.p.l. H BO37.5 g.p.l. Wetting agent (sodium salt of lauryl sulfonic acid) 0.2g.p.l.

Plating conditions Temperature F.

pH 2. Current density 50 est.

Bright nickel (Table VI):

Plating bath g-p-l. 'NiCl .6H O 206 g.p.l. H 30 37.5 g.p.1.

6 g.p.l.

1.25 ml./l.

5 mL/l.

140 F. 3.5. 50 ast.

Chromium:

Cobalt:

Plating bath- CrO 250 -g;p.l. S 2.5 g.p.l. Plating conditionsTemperature 113 F. Current density 144 a.s.f.

Plating composition- CoSO .6H O 450 g.p.l. COC12.6H2O g.p.l. Na BO 40g.p.l. Plating conditions Temperature 130 F. pH 4.2. Current density 25a.s.f. Anodes Electrolytic Before the outer nickel layer was depositedon the cobalt cobalt.

layer, the latter was given a cold 'water rinse.

Cobalt-tungsten alloy:

Plating composition CoCl .6H O 102 g.p.l. N212W042H2O g.p-l- NaK'C H OAH O g.p.l. NH Cl 50 g.p.l. Plating conditions- Temperature 195 F. pH 859. Current density a.s.f. Anodes Electrolytic cobalt. AgitationMechanical stirrer.

Before the outer nickel layer was deposited on thecobalttungsten alloylayer, the latter -.was :given a cold water rinse.

Cobalt-nickel alloy plating:

Plating bath for dull plate- NiSO .7H O 185 g.p.l. NiCl .6H O 44 g.p.l.C0SO4.7H2O 143 g.p.l. H BO 37.5 g.p.l. Wetting agent sodium salt oflauryl sulfonic acid) 0.2 g.p.l. Plating conditions- Temperature 140 F.pH 2.0. Current density 50 a.s.f. Anode Electrolytic nickel. Depositappearance Dark matte. Analysis of deposit 53.3% co.

halt.

Plating bath for bright plate- Same composition as for dull plate butadded- Brightening agent (a mixture of saccharin, benzene sulfonamideand paratoluene sulfonamide)- 6 g.p.l. Luster-producing agent containingpyrodininm and quinolinium compounds 1.25 ml./l. Wetting agent (amixture of agents exemplified by a sodium salt of lauryl sulfoacetateand a sodium salt of monolauryl ether of ethylene glycol monosulfate) 5ml./l.

Before the outer nickel layer was deposited on the tin layer, the latterwas given a cold water rinse.

A. silver strike was ,first applied Silver strike solution AgCN 5 gpl Ag4 gpl NaCN gpl Silver strike conditions Temperature 76 F. Currentdensity 20 a.s.f.

Anodes Silver. Time 30 seconds. Plating composition- AgCNv 30.3 g.p.l.Ag 24.6 g.p.l. KCN 54.8 g.p.l. K Co3 g.p.l. Plating conditions-Ternperature 76 F. Current density 10 a.s.f. Anodes Silver.

Before the outernickel layer was deposited on the layer 'of silver, thelatter was subjected to a cold Water rinse.

Palladium:

Plating solution Catholyte [Pd(NH );;]Cl 40 g.p.l. NH OH 35 cc./ 1. NHCl 1O g.p.l. Anolyte- (NH4)2CO3 g.p.l. (NH4)2SO4 g.p.l. NH OH 5O cc./l.Plating conditions Temperature 70 F. pH 9-10. Current density 7 a.s.f.Anodes Platinum sheets. Diaphragm Porous Alundurn cup.

Before the outer nickel layer was deposited on the layer of palladium,the latter was given a cold water rinse.

Plating composition Lead 32 oz./gal. Lead fiuoborate 59 oz./ gal. Boricacid 3.8 oZ./gal. Hydrofluoric acid (free) 5.4 0z./gal. Platingconditions- Temperature 76 F. Current density 16.5 a.s.f. AnodesChemical lead.

CompoSition diluted in half with distilled water and 0.1 g.p.l. of glueadded.

75 Before the outer nickel layer was deposited on the layer 13 of lead,the latter was subjected to the following pretreatment: '(1) waterrinsed, (2) anodically treated in alkaline solution for 15 seconds at 6volts and at a temperature of 76 F. The solution contained 50 g.p.l. ofNaOAc.

The present invention is particularly applicable to providing compositeelectrodeposited coatings on structural metals which are susceptible toatmospheric attack when exposed by themselves. Such foundation metalsare copper, zinc, aluminum, brass, etc., and alloys such as steel, e.g.,carbon steels and low alloy steels containing phases associated withalpha iron, etc. The composite electrodeposits of the invention aresuitable for use in both industrial and marine atmospheres.

Although the phenomena underlying the improved results which areobtained in carrying out the present invention are very complicated andare not fully understood, it is believed that the improvements fiowingfrom the present invention are related to the use as the intermediatelayer of the special composite coating a metal having a definitegalvanic relationship to nickel. Thus, metals such as Zinc, iron andiron-nickel alloys are too strongly anodic to nickel and areunsatisfactory for purposes of the present invention. Copper also isunsatisfactory for purposes of the present invention, although theelectrochemical explanation therefor is obscure. Thus, copper appears toact cathodically to nickel at some times and anodic at other times.

The beneficial effects brought about by the invention are notexplainable on the simple basis of interrupting the continuity of thenickel coating, although this factor is involved. The available dataindicate that the kind of metal used in the intermediate layer and thethickness of the intermediate layer are of primary importance incarrying out the invention to produce protective and decorativeelectrodeposited coatings having a thickness of about 1 mil, e.g., atleast about 0.25 mil to 3 or 4 mils. The data also indicate that themetals cobalt, alloys thereof with tungsten and nickel, lead, tin,silver and palladium meet the requirements for producing improvedresults in composite electrodeposited decorative and protective coatingsin accordance with the invention.

The preferred composite or sandwich electrodeposited coatings describedhereinbefore are satisfactory for the usual commercial applications suchas automotive bumpers and trim where a protective and/or decorativecoating resistant to atmospheric corrosive effects is required. Otherapplications include trim and outer shells for electrical appliances andthe like, metal furniture, etc., where a bright, attractive metal finishwhich is durable in service is required.

Metal coatings, e.g., nickel coatings, for use in accordance with theinvention advantageously are produced by electrodeposition. However, itis to be understood that chemically deposited nickel coatings and cobaltcoatings such as those described in the Brenner et al U.S. Patents Nos.2,532,283 and 2,532,284, coatings produced by high vacuum vaporizing andby thermal decomposition of metal carbonyls, such as nickel carbonyl,may also be employed to produce metal layers in accordance with theinvention.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

We claim:

1. As a new article of manufacture, a metal article having firmly bondedto the surface thereof a protective and decorative composite metalcoating, said coating consisting of a foundation layer of nickel about0.1 to about 2 mils thick deposited on said metal surface, an electro-14 deposited metal layer of cobalt with up to 20% tungsten and up tonickel about 0.01 mil to about 0.3 mil thick applied to said nickellayer, a layer of nickel about 0.5 to 2 mils thick applied to said metallayer, and an outer decorative layer of electrodeposited chromium, saidcomposite coating being characterized by an improved decorative andprotective effect as compared to a coating having a single nickel layerof the same thickness.

2. As a new article of manufacture, a metal article having firmly bondedto the surface thereof a protective and decorative composite metalcoating, said coating consisting of a foundation layer of nickel about0.1 to about 2 mils'thick deposited on said metal surface, anelectrodeposited cobalt layer about 0.01 to about 0.1 mil thick appliedto'said nickel layer, a layer of nickel about 0.5 to '2 mils thickapplied to said cobalt layer, and an outer decorative layer ofelectrodeposited chromium, said composite coating being characterized byan improved decorative and protective eifect as compared to a coatinghaving a single nickel layer of the same thickness.

3. As a new article of manufacture, a metal article having firmly bondedto the surface thereof a protective and decorative composite metalcoating, said coating consisting of a foundation layer of nickel about0.1 to about 2 mils thick deposited on said metal surface, a layer ofelectrodeposited dissimilar metal about 0.01 mil to about 0.3 mil thickfrom the group consisting of tin, lead, silver, palladium, cobalt andalloys of cobalt with up to 20% tungsten and up to 90% nickel applied tosaid nickel layer, a layer of nickel about 0.5 to 2 mils thick appliedto said dissimilar metal layer, and an outer decorative layer ofelectrodeposited chromium, said composite coating being at least about0.25 mil thick and being characterized by an improved decorative andprotective efiect in the deposited condition as compared to a coatinghaving a single nickel layer of the same thickness.

4. As a new article of manufacture, a metal article having firmly bondedto the surface thereof a protective and decorative composite metalcoating at least about 1 mil and up to about 4 mils thick, said coatingconsisting of a plurality of electrodeposited nickel layers wherein theoutermost nickel layer is about 0.1 to 2 mils thick and at least oneintermediate layer of electrodeposited dissimilar metal from the groupconsisting of tin about 0.05 to about 0.3 mil thick, lead about 0.1 toabout 0.3 mil thick, silver about 0:05 to about 0.2 mil thick, palladiumabout 0.05 to about 0.2 mil thick, cobalt about 0.01 to about 0.1 milthick, an alloy of cobalt with up to 20% tungsten about 0.05 to about0.2 mil thick and an alloy of cobalt with up to 90% nickel about 0.1 toabout 0.3 mil thick adherently contacting two of said nickel layers,said composite coating being characterized by an improved protective anddecorative effect in the deposited condition as compared to a coatinghaving a single nickel layer of the same thickness.

5. In the method for applying a protective and decorative compositemetal coating upon a metal article, the improvement which consists ofdepositing a nickel layer about 0.1 to 2 mils thick upon a metalarticle, electrodepositing a dissimilar metal layer from the groupconsisting of tin about 0.05 to about 0.3 mil thick, lead about 0.1 toabout 0.3 mil thick, silver about 0.05 to about 0.2 mil thick, palladiumabout 0.05 to about 0.2 mil thick, cobalt about 0.01 to. about 0.1 milthick, alloys of cobalt with up to about 20% tungsten about 0.05 toabout 0.2 mil thick and alloys of cobalt with up to 90% nickel about 0.1to about 0.3 mil thick upon said nickel layer and depositing a nickellayer about 0.5 to about 2 mils thick upon said dissimilar metal layerto provide a coated metal article having a composite protective anddecorative coating characterized by an improved protective anddecorative effect as compared to a similar metal article having thereona single nickel layer of the same thickness.

6. In the method for applying a protective and decorative compositemetal coating upon a metal :aaticle, the

improvement which consists of depositing a nickel layer about 0.1 toabout 2 mils thick upon said article, electrodepositing upon said nickellayer a layer of dissimilar metal about 0.01 to about 0.3 mil thick fromthe group consisting of tin, lead, silver, palladium, cobalt and alloysof cobalt with up to 20% tungsten and up to 90% nickel, depositing anickel layer about 0.5 to about 2 mils thick upon said dissimilar metallayer and depositing an outer chromium layer about to 20 micro-inchesthick upon the composite coating to provide a coated metal articlehaving a composite protective and decorative coating characterized by animproved decorative and protective etfect as compared to a similarcoated article having a single nickel layer of the same total nickelthickness.

7. In the method for applying a decorative and protective compositemetal coating upon a metal article, the improvement which consists ofdepositing a nickel layer about 0.1 mil to about 2 mils thick upon saidarticle, electrodepositing upon said nickel layer an intermediate layerabout 0.01 to about 0.3 mil thick of cobalt with up to 20% tungsten andup to 90% nickel, depositing on said intermediate layer a nickel layerabout 0.5 to about 2 mils thick, depositing an outer chromium layer toprovide a decorative and protective composite coating characterized byan improved decorative and protective effect in the deposited conditionas compared to a coating having a single nickel layer of the same totalnickel thickness.

8. In the method for applying a protective and decorative compositemetal coating upon a metal article, the improvement which consists ofdepositing a nickel layer about 0.1 to 2 mils thick upon a metalarticle, electrodepositing a cobalt layer about 0.01 to about 0.1 milthick upon said nickel layer, depositing a nickel layer about 0.5 toabout 2 mils thickupon said cobalt layer and depositing an outerchromium layer about 10 to 20 microinches thick to provide a coatedmetal article having a composite protective and decorative coatingcharacterized by an improved efiect as compared to a similar metal ar-16 ticle having thereon a single nickel layer of the same totalthickness.

9. As a new article of manufacture, a metal article having firmly bondedto the surface thereof a composite metal coating at least about 1 miland up to about 4 mils thick, said coating consisting of a plurality ofelectrodeposited nickel layers wherein the outermost nickel layer isabout 0.1 to 2 mils thick, and at least one electrodepositedintermediate layer about 0.05 to about 0.2 mil thick of acobalt-tungsten alloy containing about 10% to 20% tungsten and thebalance essentially cobalt adherently contacting two of said nickellayers, said composite coating being characterized by an improvedprotective effect in the deposited condition as compared to a coatinghaving a single nickel layer of the same total thickness.

10. As a new article of manufacture, a metal article having firmlybonded to the surface thereof a composite metal coating at least about 1mil and up to about 4 mils thick, said coating consisting of a pluralityof electrodeposited nickel layers .wherein the outermost nickel layer isabout 0.1 to 2 mils thick, and at least one electrodepositedintermediate layer about 0.1 mil to about 0.3 mil thick of acobalt-nickel alloy containing about to nickel with the balanceessentially cobalt adherently contacting two of said nickel layers, saidcomposite coating being characterized by an improved protective effectin the deposited condition as compared to a coating having a singlenickel layer of the same total thickness.

References Cited in the file of this patent UNITED STATES PATENTS289,337 Dunn Nov. 27, 1883 1,787,477 Hanley et al. Jan. 6, 19312,428,033 Naohtman Sept. 30, 1947 2,658,266 Du Rose et al Nov. 10, 19532,900,707 Brown Aug. 25, 1959 UNITED STATES PATENTv OFFICE CERTIFICATEOF CORRECTION Patent No, 3 OO9 238 November 21 1961 Waclaw A0 Wesley etal0 It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

- C-,old mn ggg l in lO for "lO-micro-inches" read l0 micro-inches lines21 and 22 for "atmosphereic" read atmospheric 5 column 7 line 11 for'"speciments" read specimens line 29 for "sliver" read me silver -3 line57 for "protactive" read protective column ll line 5O insert an openparenthesis before "sodium"; line 59 for "53.3% 00. read 533% 00- line68 for pyrodininm read pyridinium Signed and sealed this 1st day of May1962.

(SEAL) Attestz' ERNEST W, SWIDER DAVID L. LADD Attesting OfficerCommissioner of Patents

1. AS A NEW ARTICLE OF MANUFACTURE, A METAL ARTICLE HAVING FIRMLY BONDEDTO THE SURFACE THEREOF A PROTECTIVE AND DECORATIVE COMPOSITE METALCOATING, SAID COATING CONSISTING OF A FOUNDATION LAYER OF NICKEL ABOUT0.1 TO ABOUT 2 MILS THICK DEPOSITED ON SAID METAL SURFACE, ANELECTRODEPOSITED METAL LAYER OF COBALT WITH UP TO 20% TUNGSTEN AND UP TO90% NICKEL ABOUT 0.01 MIL TO ABOUT 0.3 MIL THICK APPLIED TO SAID METALLAYER, AND AN 0.5 TO 2 MILS THICK APPLIED TO SAID METAL LAYER, AND ANOUTER DECORATIVE LAYER OF ELECTRODEPOSITED CHROMIUM, SAID COMPOSITECOATING BEING CHARACTERIZED BY AN IMPROVED DECORATIVE AND PROTECTIVEEFFECT AS COMPARED TO A COATING HAVING A SINGLE NICKEL LAYER OF THE SAMETHICKNESS.